The present invention relates to a rotating electric machine, a motor-driven vehicle which mounts the same thereon, and a method for inserting a resin into a stator iron core in a rotating electric machine.
There have been conventionally known rotating electric machines disclosed in, for example, Patent Literature 1 (Japanese Patent Application Laid-open No. 11-178259) and Patent Literature 2 (Japanese Patent Application Laid-open No. 2000-341889). These Patent Literatures disclose a rotating electric machine provided with a stator including a yoke (or referred to as a core back or a yoke iron core) and a tooth (or referred to as a tooth iron core) which is formed separately from the yoke and disposed in the yoke with a winding wound in a concentric manner (for example, see page 6 and FIGS. 1 to 6 of Patent Literature 1 or page 4 and FIGS. 1, 4, 6 and 7 of Patent Literature 2).
Furthermore, Patent Literature 1 discloses a stator fabricating method in which a bobbin wound with a winding is compressed, thereby forming a coil mold, which is then fitted to the tooth, and then, the tooth is fitted to the core back (for example, see page 10, FIGS. 3, 7 and 15 of Patent Literature 1). Patent Literature 2 discloses that a winding frame is inserted into the tooth by the use of an insulating member, a winding conductor is wound around the tooth, and the tooth wound with the winding conductor is coupled to the yoke (for example, see page 4 and FIGS. 2 to 6 of Patent Literature 2).
In recent years, an environmentally friendly car such as an electric car or a hybrid car has been prevailed in order to reduce an adverse influence of exhaust gas, which is discharged from a car, on the terrestrial environment. The number of such cars has been increased year after year. In order to increase the percentage of the environmentally friendly car, it is preferable to provide an environmentally friendly car of excellent traveling performance at a low cost.
In view of this, a rotating electric machine used as a drive source for an environmentally friendly car need be reduced in size and weight and suitable for rotation at a high speed since the rotating electric machine must be mounted on a vehicle. Moreover, high efficiency is required for the rotating electric machine in such a manner as to secure a sufficient traveling distance by one electric charging with the capacity of batteries while the number of batteries to be mounted on the vehicle is limited. Additionally, a high output is required for the rotating electric machine in such a manner as to output a large torque in low and middle speed regions. In addition, cost reduction is required for the rotating electric machine in such a manner as to provide an environmentally friendly car at a low cost.
The rotating electric machine disclosed in Patent Literature 1 or 2 adopts a system in which the core constituting the stator is formed of the yoke and the tooth in separation, wherein the winding is wound around the tooth, which is then disposed in the yoke, that is, a concentrically winding system with the separate cores, as described above, thereby enhancing the winding density of the winding inside of a slot. Consequently, the turning number of the winding inside of the slot is increased so as to increase the current density of the winding inside of the slot in the rotating electric machine disclosed in Patent Literature 1 or 2, and therefore, it is possible to achieve the miniaturization, the light weight and the high output of the rotating electric machine. Furthermore, the reduced cost and high efficiency of the rotating electric machine can be achieved in the rotating electric machine which adopts the system of the concentric winding with the separate core, as disclosed in Patent Literature 1 or 2 and as described above.
However, a copper loss of the winding inside of the slot is increased to increase heat generation in the winding when the current density of the winding inside of the slot is increased by increasing the turning number of the winding inside of the slot. Therefore, it is necessary to enhance the cooling efficiency of the winding. The heat generated in the winding is transmitted to the core via a slot insulator between the winding and the slot (or referred to as a slot liner) and air present between the winding and the tooth, and then, is radiated to the air or cooling water as a cooling medium from the core. The slot insulator and the air are thermal resistances. Consequently, the thermal resistance such as the slot insulator and the air need be reduced so that the heat generated in the winding can be easily transmitted to the core in order to enhance the cooling efficiency of the winding.
With regard to this point, the winding has been previously wound around the bobbin to form a coil mold, and then, the coil mold is fitted to the tooth in the rotating electric machine disclosed in Patent Literature 1, as described above. In this system, it is general that the dimension of the inner diameter of the bobbin is made greater than that of the outer diameter of the tooth in such a manner that the coil mold can be readily fitted to the tooth. Consequently, since the adhesiveness between the coil mold and the tooth is weak even if the thickness of the bobbin can be reduced so as to reduce the thermal resistance in the rotating electric machine disclosed in Patent Literature 1, an air layer is liable to be formed between the coil mold and the tooth, thereby increasing the thermal resistance. To solve this problem, it is conceived that the dimensional precision is enhanced to strengthen the adhesiveness between the coil mold and the tooth in the rotating electric machine disclosed in Patent Literature 1. However, in turn, the productivity is reduced, thus increasing a production cost.
In the meantime, an insulating member is inserted into the tooth so as to form a winding frame, and then, the winding is wound around the winding frame in the rotating electric machine disclosed in Patent Literature 2, as described above. In this system, the insulating member is brought into close contact with the tooth, so that an air layer is hardly formed between the insulating member and the tooth. Thus, this configuration is advantageous in reducing the thermal resistance. However, upper and lower dies are used as the mold when the insulating member is inserted into the tooth in the rotating electric machine disclosed in Patent Literature 2, thereby preventing the achievement of the satisfactory thickness precision of the insulating member inserted into the tooth. From experiments carried out by the present inventors, it was found that it was difficult to uniformly reduce the thickness of the insulating member in the tooth to 0.5 mm or smaller in the insulating member inserting method by the use of the upper and lower dies, as in the rotating electric machine disclosed in Patent Literature 2.